1. Field of the Invention
The invention relates to a pump for fluids or fluid-like media, in particular for foodstuffs or articles of consumption as well as medicines or cosmetics, with a housing, an inlet, an outlet, a pump operating chamber with a pump duct, an intake chamber, a conveying area, an outlet chamber, and with a rotor which has a rotor shaft and which can be rotated by a drive and which is releasably connected to a drive shaft while forming connecting boundary faces with the aid of a fastener and which has a pump element cylindrical on its external peripheral face and rotating in the pump duct and with undulating boundary faces extending radially from the rotor shaft, in which case the pump duct is cylindrical at least in the conveying area and is provided at least in the conveying area with a pump-duct end face against which the greatest radial points of the pump element rest in a sealed manner, and a shut-off element displaceable axially with respect to the rotor axis is provided in the pump operating chamber, the shut-off element sealing off the pump duct between the inlet and the outlet and comprising opposed sealing faces which rest in a sealed manner against the undulating boundary faces of the pump element, so that during the rotation of the rotor the shut-off element follows the undulating movement of the boundary faces of the pump element, and with a seal which seals off the media-conveying pump chambers from the housing.
2. Description of the Prior Art
A pump of this type is known from DE 34 18 708 A1. In this case the pump element of the rotor is integrally joined to a hollow cylindrical rotor shaft and a hub respectively. The hub is pressed axially onto a hub pin formed with the drive shaft and is connected in a rotationally fixed manner to the hub pin or the drive shaft by means of feather keys engaging in grooves in the hub and the hub pin. In order to fix the hub axially to the pump element on the hub pin the hub pin is provided at its free end with an attachment thread onto which is screwed a mounting and retaining nut which in the tightened state presses the hub against a stop provided at the rear and thus prevents axial displacement. With this design it is not possible to prevent undesired bacteria and/or fungi from eventually becoming established, which can lead to a corresponding contamination of the pumped medium. This is particularly serious for those pumped media whose handling and transportation have to meet rigorous safety and hygiene conditions, i.e. for example for foodstuffs and articles of consumption as well as for medicines and cosmetics. In addition, if the mounting and retaining nut is not properly tightened it can become unscrewed. As a result, this can lead to breakdowns in the pump operation and even to the destruction of essential pump parts in conjunction with complete failure of the pump.